Diagnosing a bad TPS?

[TimGinCentralNJ]

Guys-
I just had to drop almost $1800 at my indy's place trying diagnose my ongoing front end alignment issues....finally solved (2 bent spindles), but "now for something completely different" as they say...

Noticed my throttle not responding when I 'blip' it between down-shifts. Idle is smooth as silk, but now running around 1k vs the normal 750 RPMs. Driving at low RPMs is fine, so I don't **think** it's a vacuum leak.
Throttle response seems totally normal while driving, even while accelerating all the way up to redline, but whenever I tap the pedal, either I get a slight stumble, or no response whatsoever. Will test this again when cold to see if maybe temp-related.

Maybe a dirty/bad TPS? Any direction would be appreciated.

TIA,
Tim G. (quickly losing sense of humor)
'91 535iM

[ryan roopnarine]

BECAUSE you said that the idle is higher than normal...as you don't have the same hidden labyrinthe of hoses that can get kinked as on my m50 one (idle would run high to compensate for lack of air....doesn't make sense, but that is what the computer, and it did), i'd say clean yours out and see what happens..my hoses aren't 100% straight, and on a rare occasion, a feather tapping of the throttle takes about 500 ms before the car will "kick" into revving. hoping to fix hoses when i take my intake off to clean it.

[TimGinCentralNJ]

...but I've done some more investigating on this. I've verified this is also occurring when the motor is cold, and that it seems to be running rich. To clarify, it's not that it takes slightly longer when I 'blip' the accelerator...it simply doesn't register at all. Sounds a little more 'extreme' than what happened to you.

From reading various posts on this, I'm now wondering if either my o2 sensor might be on the way out (causing me to run rich w/ a higher idle, thus throwing everything else off), or maybe I really do have an air-leak. Since I've never had one on a bimmer, I guess I shouldn't assume it'll behave the same way that my '89 GTi did when it had one. Definitely cheap 'n easy enough to verify, plus I have no idea when/if my bellows were even replaced.

Keep ya' posted!

Thanks again,
Tim G
'91 535iM


BECAUSE you said that the idle is higher than normal...as you don't have the same hidden labyrinthe of hoses that can get kinked as on my m50 one (idle would run high to compensate for lack of air....doesn't make sense, but that is what the computer, and it did), i'd say clean yours out and see what happens..my hoses aren't 100% straight, and on a rare occasion, a feather tapping of the throttle takes about 500 ms before the car will "kick" into revving. hoping to fix hoses when i take my intake off to clean it.

[Martin in Bellevue]

Clock it to hear the click when throttle just returns to idle. It is easy to check.

[winfred]

a dirty throttle body can also hold it open, i've seen em click and not work, the center wire is common, one of the outer wires is wide open switch and the other is closed throttle, you want contenuity in their respective positions from the center wire to the outer

[Crusty nz]

.I was 90% through posting an explanation then i pushed the wrong key and lost it.But try a used tps at an inde and see how you go.mine was showing fine on his scanner but was fixed when I convinced him to try another.Mail me if you want the long winded story .Good luck.

[Paul in NZ]

;)